Run Prometheus on a different port, optionally. (#3274)

synapse/app/appservice.py

@@ -94,6 +94,13 @@ class AppserviceServer(HomeServer):
                         globals={"hs": self},
                     )
                 )
+            elif listener["type"] == "metrics":
+                if not self.get_config().enable_metrics:
+                    logger.warn(("Metrics listener configured, but "
+                                 "collect_metrics is not enabled!"))
+                else:
+                    _base.listen_metrics(listener["bind_addresses"],
+                                         listener["port"])
             else:
                 logger.warn("Unrecognized listener type: %s", listener["type"])